#include<iostream>
#include<vector>
#include<queue>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<cstdio>
#include<algorithm>
#define debug(a) cout<<#a<<"="<<a<<endl;
using namespace std;
const int maxn=1e5;
typedef long long LL;
inline LL read(){LL x=0,f=1;char ch=getchar();	while (!isdigit(ch)){if (ch=='-') f=-1;ch=getchar();}while (isdigit(ch)){x=x*10+ch-48;ch=getchar();}
return x*f;}
int main(void)
{
  ///cin.tie(0);std::ios::sync_with_stdio(false);
  LL n;cin>>n;
  LL l=1;LL r=n;
  LL midpos=0;
  ///cout<<"? "<<l<<" "<<r<<endl;
 /// cin>>midpos;
  bool flag=1;
  while(l<r){
    LL mid=(l+r)>>1;
    cout<<"? "<<l<<" "<<r<<endl;cout.flush();
    cin>>midpos;
    cout<<"? "<<mid<<" "<<r<<endl;cout.flush();
    LL rx;cin>>rx;
    cout<<"? "<<l<<" "<<mid<<endl;cout.flush();
    LL lx;cin>>lx;
    if(r-l==1){
        if(midpos==rx){
            cout<<"!"<<" "<<l<<endl;cout.flush();
            flag=0;
            break;
        }
        else{
            cout<<"!"<<" "<<r<<endl;cout.flush();
            flag=0;
            break;
        }
    }
    if(rx>midpos){
        r=mid-1;
    }
    else{
        l=mid+1;
    }
  }
///if(flag==1) cout<<"!"<<" "<<l<<endl,cout.flush();
return 0;
}
